When supplying the electrical equipment within the internal contaminated zone of a protective shell, it is essential to bring the conductor into the zone in such a way as to prevent the escape of the contaminated medium (vapour-gas mixtures, chemically aggressive vapours, radioactive radiation, etc.), i.e. to ensure adequate biological shielding and protection of the personnel and environment.
When dealing with heavy currents, it is necessary to combine a high current-carrying capacity of the conductor with a high resistance to the effect of continuously applied high temperatures under normal operating conditions and the short-term effect of still higher temperatures and mechanical stresses under emergency conditions.
Known in the art is a through insulator (cf. Federal Republic of Germany Printed Patent Specification No. 1,640,495) representing a closed system in the form of a steel tube closed by end flanges and placed within the body of the protective shell. The tube contains rigidly fixed current-carrying conductors.
Such an arrangement of the conductors does not provide for sufficient operational reliability at load currents of several hundreds of amperes and higher, nor does it rule out the possibility of the conductors coming into contact or closely approaching one another, thus giving rise to an arc discharge and breakdown of the insulator due to the electrodynamic forces set up by the short-circuit current. The continuous and short-time effect of high temperatures occurring under emergency conditions in the absence of thermal compensation for the change in linear dimensions of the conductors leads to a loss of sealing of the insulator.
Also known is a device for passing the conductors of electrical and power installations through a protective shell separating a clean zone from a contaminated one (cf., U.S. Pat. No. 3,801,722), comprising a hollow metal casing in the form of a tube with end flanges fixed in the body of the protective shell, the latter having a metal shield attached to the side within the contaminated zone. The metal casing contains a main insulating through element having at least one through hole for the conductor passed from the clean zone into the contaminated one. The main insulating through element is composite--its parts, where the conductors are brought out of the insulating element, are made of an epoxy resin, and the remaining parts are of a silicone elastomer. The conductors brought into the main insulating element through the end flanges are the conductors of a multi-core cable. The cable conductors are arranged and positioned rigidly by the monolithic material of the composite parts of the main insulating through element.
The rigid positioning of the conductors within the main insulating through element does not allow one to compensate for the change in linear changes during the passage of heavy short-circuit currents and high temperature rise impairing the mechanical strength of the device.
Sealing of the known device is achieved in the mid part of the main insulating through element, but is insufficient at the entry and exit of the conductors.
The composite structure of the main insulating through element made up of different polymer materials also worsens the reliability of the device under emergency conditions and shortens its service life.